Synlett 2011(6): 844-848  
DOI: 10.1055/s-0030-1259921
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Concise and Cascade Synthesis of Batracylin and Substituted Isoindolo-[1,2-b]quinazolin-12(10H)-ones

R. Shankara, Manoj Balu Wagha, M. V. Madhubabua, N. Vembub, U. K. Syam Kumar*a
a Technology Development Centre, Custom Pharmaceutical Services, Dr. Reddy’s Laboratories Ltd, Miyapur, Hyderabad, 500049, India
Fax: +91(40)23045439; Fax: +91(40)23045438; e-Mail: syam_kmr@yahoo.com;
b Urumu Dhanalakshmi College, Tiruchirappalli 620019, India
Further Information

Publication History

Received 28 October 2010
Publication Date:
16 March 2011 (online)

Abstract

A concise, highly convergent, and practical synthesis of the clinical-phase anticancer agent batracylin in a two-stage process in excellent yield is described. The B and C rings of this tetracyclic heterocycle are constructed by cascade cyclization of 5-nitro-2-aminobenzyl alcohol with 2-cyanomethyl benzoate in trifluoroacetic acid in good yield in a single-pot reaction. A plausible mechanism for the cascade reaction is also proposed. As part of these studies, a range of batracylin derivatives with different substituents on the C and D rings are synthesized.

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A solution of methyl 2-cyanobenzoate (0.5 g, 0.003 mol), 2-aminophenylmethanol (0.57 g, 0.0047 mol) in TFA (10 mL) was refluxed for 10-12 h, and the progress of the reaction was monitored by TLC. After complete disappearance of the starting material, the reaction was quenched with ice water and the aqueous layer extracted with CH2Cl2 (2 × 10 mL). The combined extracts washed with aq NaHCO3 (10%, 25 mL) dried over anhyd Na2SO4, filtered, and concentrated under vacuum. The crude product was then purified by column chromatography using CH2Cl2 as an eluent; yield 0.43 g (62%).

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Isoindolo [1,2- b ]Quinazolin-12(10 H )-one (12)
Yield 62%; mp 186 ˚C (lit. 175-177 ˚C);8 IR (KBr): 1724, 1650 cm. ¹H NMR (400 MHz, CDCl3): δ = 8.08 (d, J = 7.6 Hz, 1 H, ArH), 7.90 (d, J = 6.7 Hz, 1 H, ArH), 7.74-7.63 (m, 2 H, ArH), 7.51 (d, J = 8.0 Hz, 1 H, ArH), 7.34-7.18 (m, 3 H, ArH), 5.00 (s, 2 H, CH2) ppm. ¹³C NMR (100 MHz, DMSO-d 6): δ = 166.2, 148.7, 140.0, 134.0, 133.2, 132.4, 130.1, 128.4, 127.4, 127.3, 127.2, 122.8, 121.9, 121.2, 40.2 ppm. MS: m/z (%) = 235.2 [M + H]+. Anal. Calcd for C15H10N2O (234.2): C, 76.91; H, 4.30; N, 11.96; O, 6.83. Found: C, 76.83; H, 4.25, N, 4.26, O, 6.70.

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8-Bromoisoindolo[1,2- b ]quinazolin-12(10 H )-one (24)
Yield 63%; mp 214 ˚C. IR (KBr): 1731, 1645 cm. ¹H NMR (500 MHz, DMSO-d 6): δ = 8.02 (d, J = 7 Hz, 1 H, ArH), 7.90 (d, J = 7 Hz, 1 H, ArH), 7.84-7.77 (m, 2 H, ArH), 7.57 (s, 1 H, ArH), 7.51 (dd, J = 8.2, 1.5 Hz, 1 H, ArH), 7.34 (d, J = 8.5 Hz, 1 H, ArH), 4.93 (s, 2 H, CH2) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 165.9, 149.2, 139.3, 133.7, 133.1, 132.4, 131.1, 129.8, 128.8, 124.4, 122.7, 121.9, 119.5, 40.7 ppm. MS: m/z (%) = 313.1 [M + H]+. Anal. Calcd for C15H9BrN2O (311.99): C, 57.53; H, 2.90; N, 8.95; O, 5.11. Found: C, 57.48; H, 2.85; N, 8.85; O, 5.1. 7-Fluoroisoindolo[1,2- b ]quinazolin-12(10 H )-one (25) Yield 57%; mp 213 ˚C. IR (KBr): 1729, 1646 cm. ¹H NMR (400 MHz, CDCl3): δ = 8.06 (d, J = 7.2 Hz, 1 H, ArH), 7.92 (d, J = 6.8 Hz, 1 H, ArH), 7.75-7.69 (m, 2 H, ArH), 7.22 (dd, J = 2.4, 9.6 Hz, 1 H, ArH), 7.19-7.12 (m, 1 H, ArH), 6.98-6.93 (m, 1 H, ArH), 4.95 (s, 2 H, CH2) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 166.8, 149.9, 142.1, 133.0, 132.6, 132.3, 131.6, 131.1, 130.4, 127.8, 127.7, 123.5, 123.2, 122.3, 40.3 ppm. MS: m/z (%) = 253.2 [M + H]+. Anal. Calcd for C15H9FN2O (252.07): C, 71.42; H, 3.60; N, 11.11; O, 6.34. Found: C, 71.34; H, 3.50; N, 11.01; O, 6.29. 9-Methylisoindolo[1,2- b ]quinazolin-12(10 H )-one (26) Yield 54% mp 243 ˚C. IR (KBr): 1721, 1650 cm. ¹H NMR (400 MHz, DMSO-d 6): δ = 8.04 (d, J = 6.8 Hz, 1 H, ArH), 7.92-7.78 (m, 3 H, ArH), 7.26-7.24 (m, 2 H, ArH), 7.14-7.10 (m, 1 H, ArH), 4.85 (s, 2 H, CH2), 2.49 (s, 3 H, CH3) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 166.8, 148.4, 139.8, 135.4, 134.1, 132.8, 132.0, 130.4, 129.3, 128.3, 125.7, 123.1, 122.3, 119.8, 39.4, 18.1 ppm. MS: m/z (%) = 249.2 [M + H]+. Anal. Calcd for C16H12N2O (248.09): C, 77.40; H, 4.87; N, 11.28; O, 6.44. Found: C, 77.32; H, 4.78; N, 11.19; O, 6.35.
7,8-Difluoroisoindolo[1,2- b ]quinazolin-12(10 H )-one (27) Yield 53%; mp 278 ˚C. IR (KBr): 1729, 1647 cm. ¹H NMR (400 MHz, CDCl3): δ = 8.04 (d, J = 7.6 Hz, 1 H, ArH), 7.9 (d, J = 6.8 Hz, 1 H, ArH), 7.75-7.68 (m, 2 H, ArH), 7.34 (m, 1 H, ArH), 7.00 (t, 8.8 Hz, 1 H, ArH), 4.90 (s, 2 H, CH2) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 180.0, 158.5, 141.2, 133.2, 132.5, 130.3, 123.4, 122.4, 116.9, 115.4, 110.0, 40.3 ppm. MS: m/z (%) = 271.2 [M + H]+. Anal. Calcd for C15H8F2N2O (270.06): C, 66.67; H, 2.98; N, 10.37; O, 5.92. Found: C, 66.58; H, 2.87; N, 10.29; O, 5.83.
10-Phenylisoindolo[1,2- b ]quinazolin-12(10 H )-one (28) Yield 72%; mp 210 ˚C. IR (KBr): 1732, 1646 cm. ¹H NMR (500 MHz, DMSO-d 6): δ = 8.10 (d, J = 7.5 Hz, 1 H, ArH), 7.88-7.78 (m, 3 H, ArH), 7.49 (d, J = 7.0 Hz, 1 H, ArH), 7.35-7.21 (m, 8 H, ArH), 6.47 (s, 1 H, CH) ppm. ¹³C NMR (100 MHz, DMSO-d 6): δ = 174.8, 165.9, 153.2, 143.1, 138.9, 133.9, 133.8, 132.8, 129.7, 128.8, 128.7, 128.1, 127.8, 127.8, 127.3, 126.4, 126.2, 123.2, 122.3, 54.5 ppm. MS: m/z (%) = 311.2 [M + H]+. Anal. Calcd for C21H14N2O (310.11): C, 81.27; H, 4.55; N, 9.03; O, 5.16. Found: C, 81.20; H, 4.50; N, 8.92; O, 5.10.
10-Methylisoindolo[1,2- b ]quinazolin-12(10 H )-one (29) Yield 70%; mp 123 ˚C. IR (KBr): 2925, 1728, 1648 cm. ¹H NMR (400 MHz, CDCl3): δ = 7.98 (d, J = 7.6 Hz, 1 H, ArH), 7.81 (d, J = 7.2 Hz, 1 H, ArH), 7.64-7.57 (m, 2 H, ArH), 7.40 (d, J = 8.0 Hz, 1 H, ArH), 7.26-7.21 (m, 1 H, ArH), 7.18-7.15 (m, 1 H, ArH), 7.12 (d, J = 6.8 Hz, 1 H, ArH), 5.41 (q, J = 6.4 Hz, 1 H, CH), 1.51 (d, J = 6.4 Hz, 3 H, CH3) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 167.0, 149.9, 139.8, 134.5, 132.9, 132.0, 130.6, 128.6, 127.8, 127.7, 127.7, 127.5, 123.2, 122.1, 47.9, 23.6 ppm. MS: m/z (%) = 249.2 [M + H]+. Anal. Calcd for C16H12N2O (248.09): C, 77.40; H, 4.87; N, 11.28; O, 6.44. Found: C, 77.32; H, 4.81; N, 11.20; O, 6.36.

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8-Aminoisoindolo[1,2- b ]quinazolin-12(10 H )-one (1) Mp 280-282 ˚C (recrystallized from CH2Cl2). IR (KBr): 3474, 1688, 1645 cm. ¹H NMR (400 MHz, DMSO-d 6): δ = 7.95 (d, J = 8.0 Hz, 1 H, ArH), 7.86 (d, J = 6.8 Hz, 1 H, ArH), 7.78-7.68 (m, 2 H, ArH), 7.13 (d, J = 8.4 Hz, 1 H, ArH), 6.52 (dd, J = 2.4, 8.2 Hz, 1 H, ArH), 6.46 (s, 1 H, ArH), 5.54 (s, 2 H, NH2), 4.80 (s, 2 H, CH2) ppm. ¹³C NMR (100 MHz, DMSO-d 6): δ = 165.9, 148.8, 143.8, 134.2, 132.8, 131.3, 129.7, 129.4, 128.8, 122.8, 122.6, 121.2, 113.2, 111.7, 40.3 ppm. MS: m/z (%) = 250.2 [M + H]+. Anal. Calcd for C15H11N3O (249.09): C, 72.28; H, 4.45; N, 16.86; O, 6.42. Found: C, 72.19; H, 4.38; N, 16.80; O, 6.35.